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Full text of "The preparation of salicylic acid from phenol"

UNWERSJi^ V LiBEARIES 



Iat 514 

'Markham, J. H. 

iThe preparation of salicylic 

1 acid from phenol 




Digitized by tine Internet Arcliive 

in 2009 witli funding from 

CARLI: Consortium of Academic and Researcli Libraries in Illinois 



http://www.archive.org/details/preparationofsalOOmark 



The Preparation of Salicylic Acid 
FROM Phenol 



a thesis 



PRESENTED BY 

J. H. MARKHAM AND B. W. LEWIS 

TO THE 

PRESIDENT AND FACULTY 
OF 

ARMOUR INSTITUTE OF TECHNOLOGY 

FOR THE DEGREE OF 

BACHELOR OF SCIENCE 

IN 

CHEMICAL ENGINEERING 



MAY 29, 1919 



APPROVED 



I'lnA-^scr of C 



^(.r i.f CtKiiiicnl KiiK'iitrcrinsr 
^H\C^GO. ^^ " Dran of Cultunil Sl.iilies 



I H D S X 

PAGE 

PROBLEM 2 
OCGUEHENCE MD LETHODS OF PREPAHATIOil 3 

KOLBE'S PROCESS 7 

PHYSICAL PROPERTIES 10 

CHEMICAL PROPERTIES 14 

USES 0? SALICYLIC ACID 20 

OUR I.IETHOD OP PREPARATIOII 25 

EXPSRIMEITTAL RUIIS 30 

PURIEICATIOE 3^ 

THE CHEMISTRY OE TEE SCHMIDT METHOD 36 

COECLUSIOH ^° 

REEEREKCES ^^ 



2S1S5 



1. 



This work v;as done under the general direction 
and supervision of Professor Harry McCormack, 
for which respectful acknowledgment is hereby 
made. 



PROBIEI.I. 

Preparation of Salicylic acid from 
phenol. Using phenol as a starting substance 
to prepare the acid, to study the process and 
to purify the product. It was originally in- 
tended to start v.ith tenzol and go thru the 
synthesis of sodium phenate, tut since the 
price of phenol has reached such a lov; price, 
and since the synthesis of phenol is now more 
or less standard, the process starts with phenol 
and caustic soda. 



OCCUnRElJCE AllD LIETHODE OF PP.EPAHATIOIT . 

Ortho-hyuroxy-carboxylic acid, or 

ortho-hydroxy-'bensoic acid or ortho-hydroxy- 

c art oxy-b eri z ene . 

C H 
7 6 3 

C H . OH.COOH (1-2) 
6 4 

COOH 
H OE 

H H 

E 

The acid v.as first discovered by 
H. Piria in 16S9, by fusing salicylic alde- 
hyde v;ith potassium hydroxide. Calhours 
proved in 1843 that oil of v.intergreen is 
mainly methyl salicylate. In 1653 A. Ho f nan 
converted anthranilic acid into salicylic 
acid by means of nitrous acid. Finally Ilolbe 
and lautemann prepared it synthetically from 
phenol, sodium and carbon dioxide in 1673. 



Natural salicylic acid is 
found in many plants, usually in the form of 
methyl salicylate or oil of v.inter^reen 



C^H fOH)COOOII- 
6 4 3 



The acid may be obtained from the 
following plants: Gaulterla fragrantissima, 
Gaulteria procumbeus, Gaulteria punctata, 
Gaulterla leukocarpa, Betula lenta, Llonotropa 
hypopitis, Spiraea ulmaria, Gloria superba and 
from many other plants. The acid is also found 
in very small quantities in some grapes, strav,- 
berries, cherries and in fact in most fruits. 

Salicylic acid may be prepared by one 
of the following methods: 

1. 3y oxidation of, or by fusion vfith 
potassium hydroxide, or by electrolysis of one 
of the following substances; salicin, salicyc 
aldehyde, and saligenin. 

2. 2y fusing potassium hydroxide with 

one of the following substances; benzoic acid. 



indigo, coumarin, ortho-chlor-benzoic acid, ortho- 
toluene Bulphonio acid , ortho-cresol-sulphonic 
acid, ethyl-cresol-sulphonic acid. 

3. By heating with water ortho-diazo- 
amldobenzoic acid. 

4. By dry distillation of calciutn salt of 
anie acid or meta-oxybenzoic acid. 

5. 3y reaction of potassium permanganate 
on the potassium salt of o-cresolsulphonic acid. 

.6. By heating phenol with carbon tet- 
rachloride and alco::olic potash; p-oxybenzoic 
acid is here also obtained. 

C H OH+CCl + 6 KOE -* C H .OZ.GOOX * ZOL *■ 
6 5 4 6 4 

SHgO 

7. By oxidation of toluene ortho-phos- 
phonic acid with alkaline potassium permanganate. 

8. By distillation of sodium phenyl car- 
bonate in a current of carton dioxide with sodium 
phenate. 

9. By action of nitrous acid on anthranilic 

acid. 



10. By electrolysis of a solution of ben- 
zoic acid ii) acetic acid. 

11. By exposing a solution of benzoic acid 
to the sunlight in the presence of a ferric salt. 

1£, By passing dry carbon dioxide into a 
hot mixture of phenol and sodium. 

(Kolbe and lautemann) 



KOIBE'S PROCESS. 

This method has teen used for the manu- 
facture of salicylic acid on a large scale. 

Equivalent quantities of pure phenol 
and a concentrated solution of sodium hydroxide 
are thoroughly mixed and evaporated to dryness in 
iron vessels with constant stirring. When the 
mass is dry it is pulverized, placed in a metal 
retort and heated to 100°C while a current of 
heated dry carton dioxide is passed in. The mass 
is kept well stirred and the temperature is slow- 
ly raised to 180°G. This operation takes several 
hours. After the retort has ceen heated for some 
time the phenol begins to distill over. V/hen the 
evolution of phenol ceases, the temperature is 
raised to 200°C and the operation stopped. When 
the mass has cooled, it is dissolved in v.ater and 
the resinous substances precipitated with a miner- 
al acid, a further addition of acid precipitates 
salicylic acid, which is then purified. 

This process may be regarded as taking 



place In four stages: 

1. Phenol and sodium hydroxide form 

sodium phenate:- 

C-HpOH ^ ITaOH ^ C-H^ONa *■ H^O 
6 5 6 5 E 

E. Carton dioxide when added to the 

sodium phenate forms sodium phenyl cartonate:- 

C^H^OHa * CO^ = C^H^.OCO^.lTa 
6 5 E 6 5 E 

This stage is completed v.hen the mass is heat- 
ed to about 110°G for one hour. 

3. The sodium phenylcartonate is trans- 
formed into sodium salicylate:- 

C^H^.OCO^.lIa = C^H,.0H.C001Ia 
6 5 £ 6 4 

The COg goes into the Ortho-position tetv.-een 
the hydrogen atom and the neucleus, producing a 
caroxyl group. 

4. In the last stage the salt acts with 
some unchanged sodium phenate and sets free the 
TDhenol in the disodium salt 



C H .OH.COOIIa-C H^.OlIa = C H .Ol^Ta.COOlIa * G H^OH 
64 65 64 65 

This change takes place during the last stage of 
heating. 



10, 



physicjVI properties . 

Salicylic acid crystallizes irotn ^vater 
in long white needles, having a sweetish astrin- 
gent taste. From alcohol salicylic acid crystal- 
lizes in large colorless monoclinic prisms. 

The acid, has a specific gravity of 
1.48£ - 1.465 at 4^0; melting point 158° - 159°3. 
Pure salicylic acid dried in vacuum over sulphuric 
acid gives a melting point of 158, 5°C. Small 
amounts of p-hydroxybenzoic acid lower the melt- 
ing point. ".Vhen slov/ly heated to 200°G is sub- 
limes, and on cooling deposits in long fine 
needles; when rapidly heated to 200°C it vala- 
tilizes and the vapors undergo a partial dis- 
sociation into phenol and carton dioxide, accord- 
ing to the formula: 

? a^ k : 254.9 



l-a2 

7/here P^pressure in cm. of mercury, 
a=rdegree of dissociation. This is an irreversible 
reaction. 



11. 



Heat of comTDustion of salicylic acid 
is 5162 cal. per gram or 754990 cal. per mole- 
cule. Heat of formation from phenol 5520 cal.; 
latent heat of futic/. - 6550 cal.; heat of neu- 
tralisation of a solution of the acid with l/E 
molecule of sodium hydroxide 12910, and v.-ith 
another half molecule .810 cal. 

Salicylic acid is slightly soluble in 
cold vvater or petroleuoi ether, hut (luite soluble 
in hot water. 



0° 


1.24 


35° 


5.51 


70^ 


15.70 


5° 


1.29 


40° 


4.16 


75° 


17.55 


10° 


1.55 


45° 


4.69 


80° 


22.08 


15° 


1.64 


50° 


6.56 


85° 


27.92 


20° 


2.00 


55° 


7.44 


90° 


57.55 


25° 


2.46 


60^' 


9.00 


95° 


50.46 


30° 


2.98 


65° 


10.94 


100° 


75.07 



12. 



The acid is very soluble in chloroform, 
alcohol, ether, aceton and ethyl acetate. 
100 parts of ether dissolve at 15° 50.47 of acid 



100 
100 
100 
100 
100 
100 



absolute alcohol dissolve 49.65 of acid 



90;'o 



42.09 




SI. 20 




.97 




.50 




.10 





" aceton " 

" benzene " 

" glycerin " 

" petroleum ether " 

The solubility of salicylic acid is con- 
siderably increased in the presence of so;:ie salts: 
One part of salicylic acid in v;ater in the presence 

of 

1 part of potassium nitrate dissolves in 50 parts 
1.5 " " ammonium citrate " " 60 " 
E " " sodium sulphite " " 50 " 
E " " sodium phosphate " " 50 " 
2^5 »» " i» w " "12.5 " 



15. 



Chloroform or ether remove it from 
Vv'ater solutions. 

Salicylic acid can "be distilled in 
steam. 

The para-acid and traces of the meta- 
acid usually accompany the ortno-acid if extreme 
care is not ohserved in preparation. 





S.G. 


H. ?. 


Sol. in water 


Chloro- 
form 


PeOlg 


o-acid 












OH 

GOOH] 


1.4855' 


1580G' 


1:1000(150) ' 


Very ' 


Violet 


(;-i) 












m-acid 












OH 

COOH 


1.475 


200° 


1:106 


insol. 


Ho chani 


0-3) 












p-acid 












OH 
GOOH 

0-4) 


1.465 


• £15° 


1:126 


t 

Slight 

' ly 

T 


' Yellov; 
i flacc. 
' ppt. 



The ortho-acid is the only one of im- 



portance. 



14. 



CHEMICAL PROPiiRTIES. 

Salicylic acid is both an acid and a 
phenol. It forms three sets of salts; acid, 
"basic and neutral, as well as ethers. 

'.Vhen heated to 200° G it decomposes 

into phenol and carbon dioxide 

CgK^.OH.COOH ■= GgHg.OH * CO^ 

Heated in a closed vessel with water 
it decomposes into phenol and carbon dioxide at 
2E0°-230°; a similar decomposition takes place 
when treated with con. hydrochloric or hydrobromic 
acid, or with dil. sulphuric at 140°-1500 , or with 
con. phosphoric at 120°. 

Phosphorus trichloride gives qjI^ClPOg, 
which is decomposed by water into salicylic acid 
and phosphoric acid. When treated with phosphorous 
pentachloride and the products distilled, ortho- 
chlorbenzoylchloride is obtained. Phosphorous 
pentabromide yields raonobrom-salicylic acid, and 
this on heating with alcohol or phenol gives the 



15, 



esters of salicj^lic acid. Phosphorous oxychloride 
gives on heating salicylic anhydride. 

Salicylic acid or its salts give a deep 
violet coloration in a neutral solution v/ith fer- 
ric salts. This reaction is used for qualitative 
as well as quantitative determinations of sali- 
cylic acid. 2his test is sensitive to about 
1:550,000. Hov/ever phenol or salicylic aldehyde 
give the same test. The color is not removed 
hy acetic acid. This test fails, if for one part 
of salicylic acid there is present 365 parts of 
sodium nitrate or 36 parts of sodium chloride. 

Dry hot ammonia breaks up salicylic 
acid into phenol and carbon dioxide. 

On oxidation with potassium bichromate 
in sulphuric acid carbon dioxide and v.ater are 
produced. 

Potassium chlorate and hydrochloric 
acid oxidize it to chloranil. 

Potassium permanganate oxidizes it to 

formic acid and carbon dioxide. 



16, 



On oxidation witli potassium persul- 
phate in an alkaline solution and subsequent 
colling with an acid hydroquinone carboxylic 
acid is obtained. 

Chlorine forms mono- and di- substitu- 
tion products. 

Dil. nitric acid forms nitro-salicylic 
acid, while con, nitric acid forms picric acid. 

Sodium amalgam in the presence of 
boric acid produces salicylic aldehyde. 

On heating v/ith resorcin it gives tri- 
oxybenzophenone. 

Sodium and amyl alcohol reduce it 
chiefly to pimelic acid. 

Concentrated sulphuric acid gives mono- 
sulpho-salicylic acid. 

By heating v.ith concentrated sulphuric 
acid and potassium ferrocaynide phthallc acid is 
obtained. xhe same product is obtained when 
salicylic acid is heated vvith oxalic acid and 
glycerin. 



17, 



Y/hen salicylic acid is heated with 
"butyl alcohol and zinc chloride a homologue 
01 the acid is obtained, which on distillation 
goes into tutyl phenol. 

It cotahines v^ith diazo-hodies to form 
azo-compounds. 

nitrous acid passed into an etherial 
solution of salicylic acid gives nitro- and 
diaao-oxyhenzoic acids. 

At 210° aiiiline gives phenol and 

C.H^(OH).GOIIPhH. 
o 4 

Gyanamide and alcohol at 100° form 
urea and ortho-oxybenzoic ether. 

Phenol and stannic chloride at 120° 
give op-di-oxy'benzophenone, 

V.'ith camphor it forms a compound 

C H 0„2G, H 0, which melts at 50°. 
7 6 3 10^5 • 

On heating with soda lime phenol and 

carton dioxide are formed 

C^H, (OH) GO. OH ♦ Geo = C,H_OH - GaCO_ 
6 4 o 5 o 



16. 



Potassium persulphate added to a 
solution of salicylic acid and potassium hy- 
droxide forms a crystalline compound 

C H (CO K)OSO K 

A solution of salicylic acid and borax 
in water deposit crystals of a composition 

4 10 7 

Chloral forms with it at 140^^ 



^ 4 cue 5 

In dilute aqueous solutions "bromine 

water gives a x>recipitate of C;.Hr;Br.O, 

« -^ -^ Oct 

Iodine and potash give a red pov.der GgH^KODCOgZ. 

It forms compounds with casein, 
fihrim and albuminoid, containing about 14;j of 
the acid and having a foraiula — *^7E^11 ^^'18^^82 

2C H . It melts at 40°, and is soluble in 
7 6 S 

water to an extent of ,0051 parts in 100 parts 
of water. 



19. 



■".'.Tien taken Internally it is excreted 
as salicyluric acid or salicyl-glycocoll — 



EO, 



USES 0? SAIICYLIC ACID. 

Salicylic acid is largely used in the 
preparation of pharmaceuticals. The acid is 
also of importance in the manufacture of syn- 
thetic chemicals, such as dye stuffs. Its chief 
pharmaceutical uses are as an antirheumatic and 
as an antiseptic. Llany states and countries 
forhid its use as a food .preservative in which 
field it formally found one of its largest uses. 

The acid finds extensive use in the 
production of salicylates. V/hen ethyl alcohol 
and sulfuric or hydrochloric acid reacts with 
the salicylic acid, ethyl salicylate results. 
Llethyl salicylate, oil of wintergreen may be pre- 
pared from methyl alcohol and the acids in the 
same manner. Llethyl salicylate is extensively 
prescribed for external uses. Allyl salicylate 
which is prepared in the manner as described 
above, is used both medicinally and as a perfume. 
Phenyl salicylate, Salol , another derivative of 
the acid is a very important pharmaceutical; but 
because of its cost, other salicylates are sub- 



21. 



stituted. V/hen phosphorous oxychloride is 
allowed to react with the acid phenyl sali- 
cylate is thus formed. Acetyl salicylic acid, 
"Aspirin", is prepared from salicylic acid and 
acetyl chloride. "Aspirin finds extensive use 
in the treatment of rheumatic conditions. All 
of the Salicylic preparations taken internally, 
are used for T;he henefit of the salicylic acid 
v/hich is liberated in the decomposition of the 
compound. Quinine salicylate is one of the 
few compounds, prepared directly from the sodium 
salt. 

Among the most important salicylic 
salts vi'hich are used in the preparation of anti- 
rheumatic compounds are: tolypyrinesalicylate , 
salicylic-sulfonic acid, salicylamide, salicyl-a- 
methyl -phenyl -hydrazone and methl-acetyl-salicylate. 
It is interesting to note that in the production 
of the raethyl-acetyl-salicylate, anhydous zinc 
chloride is said to act as a catalytic agent. 



B2. 



The next important use of salicyio acid 
is in the synthesis of many important organic 
■bodies. 

The first of these "bodies to receive 
consideration is Saligenin. 



CH OH 
£ 

(y-3) 

OH 



This "body is prepared from salicylic 
acid, thru the amide, and the reduction of the 
latter with sodium amalgam in acid solutiOii. 

Trichlor-a-a-glyceric acid is pre- 
pared by the action of potassium chlorate and 
hydrochloric acid upon salicylic acid. V/hen 
salicylic acid is iodised by various methods, 
among our products are iouosalicylic acid, vhich 
on rapid heat-inr gives iodophenol, from which 
catechol can be obtained. 

^^uinol, hydroq^uii'Oiie, paradihydroxy- 
benzene, 1-4 phendiol may be synthesized from 
salicylic acid. 



25. 



First the salicylic acid is iodised 
or 'brominated so a.s to form 5 iodo- or 5 crom- 
salicylic acid which on fusion v/ith potash 
gives 2:5 dihydroxy "ceni'-oic acid. This "body on 
dry distillation yields quinol. This same tody 
may he prepared ty first nitrating the salicylic 
acid into the 5-nitro acid and then to the 5- 
amino salicylic acid, thence converting to the E-5 
dihydroxy "benzoic acid hy the diazo method. 

llote: The 5-amino-salicylic acid is best pre- 
pared by the redaction of benzeneazoealicylic 
acid. 5-lTitrosalicylic acid on heating with lime 
gives p- nitrophenol, -..hich can be reduced to p- 
amidophenol . and treated as above. 

Salicylic acid yields gentisic acid by 
direct oxidation with potassium persulphate in 
alkaline solution. 

Anisic alde?iyde: p-methoxyben::oic alde- 
hyde 

CHO 



OCH 



E4. 



This liOdy is found in the volatile oil 
from the wood and the bark of the Chione glabra. 
It cari ce prepared from salicylic acid by first 
converting to the aldehyde then thru S-methoxy- 
benzoylacetic ester. 

Euxanthone 




xhis body exists in euarthic acid or 
Indian Yellov.-. It is found in the free state 
In coloring matter resulting from decomposition. 
Upon nitration, salicylic acid yields 5-nitro 
and upon reduction forms 5-arainosalicylic acid. 
The amino- acid gives gentisic acid by the diaso 
method. 

There are numerous other bodies that 

are prepared synthetically by means of the sali- 
cylic acid and its salts. 



25, 



OUR Iffi'xHOD OP PREPAHATIOH. (4th Ruii) 

The materials used were pure sodium 

hydroxide and crystalline phenol. 120 grans 

of sodium hydroxide are dissolved in an equal 

weight of v.ater in a porcelain dish and cooled. 

This is slowly added to 260 grams of phenol in 

a shallow enameled pan, about 14xGxl". The 

mixture is well stirred up and kept cool. This 

gives a mixture v/hich is only slightly colored. 

It is now placed in the vacuum drying chest to 

ce evaporated to dryness. A vacuum of atout 2£" 

is maintained and the temperature is kept down 

to 50°-6C 2. The temperature must be just high 

enough so that the mass will barely boil. The 

temperature must ce kept low in ordei- to avoid 

charring. This is a very essential step in the 

process. 

The mass will gradually begin to 

thicken and in about three hours it will be 

completely solid. It is now removed from the 

drying chest and quickly powdered in an iron 



26, 



mortar to a fine powder. The fine material is 
nov/ placed back in the drying chest, tut the 
steam is turned off, and it is dried for about 
half an hour. 

The pov/der thus obtained is sodium 
phenate. It is pinkish Y/hite in color, somev/hat 
hygroscopic and very soluble in vvater, acetone 
or alcohol. 

'.Vhen dry the sodium phenate is placed 
in the autoclave and the lid is put on. The 
autoclave used was made of copper, about 14" 
tall and about 6" in diameter and about S/16" 
thick. The lid was furnished with a lead gasket 
and it formed a tight joint with the body of the 
autoclave. The cover had a safety valve, a 
passage for gas and a well for a thermometer. 
The lid was fastened by means of a heavy bracliet. 



27. 



Having placed the sodium phenate into 
the autoclave and the lid put in place, it is 
now tightly clamped in its seat. The gas inlet 
in autoclave cover is connected by means of heavy 
rubber tubing to an iron pipe containing calcium 
chloride. This pipe is about £' long and 1" in 
diameter; it is filled v;ith granular calcium c'nlor- 
ide protected at both ends with glass v.ool and 
wire gauze. The other end of this pipe is con- 
nected to a carbon dioxide tank cy means of extra 
heavy rubber tubing. 

The autoclave is now suspended in such 
a manner, that the bottom is immersed to a depth 
of atout 3" in running cold water. The carbon 
dioxide gas is turned on, the pressure in the auto- 
clave is not allowed to exceed 10 lbs. This is 
kept up for about an hour when the pressure is in- 
creased to 75 lbs. and at the same time the cool- 
ing is discontinued. V.lien no more carbon dioxide 
is being absorbed, the pressure is brought up to 
75 lbs. again and allowed to stand for about one 
hour. 



£8. 



The cooling during the first stages 
of the carhon dioxide ahsorhtion is quite a 
desirable feature, because the temperature tends 
to rise considerably and if the mass is not 
cooled, phenol is split off, the mass chares and 
fuses together making further absorbtion diffi- 
cult. 

A paraffin bath is nov; brought under 
the autoclave so that the bottom vdll be immersed 
in paraffin to a depth of about 5". The temper- 
ature 01 the bath is gradually raised to 120° G 
and for four hours the temperature is carefully 
kept at 120°-140°C. The temperature of paraffin 
bath must ue taken and not the temperature in 
the well in the autoclave cover. The latter 
temperature is about 50° below the temperature 
of the paraffin bath. 

At the end of the four hours the auto- 
clave is allowed to cool off. V.'hen cool the auto- 
clave is opened, the mass is transferred to a dish 
and water added. The water is brought to a boil 
and a few o.c. of con. hydrochloric acid added. 



29. 



This throws out the tarry matter and creosotic 
acids. This is separated in a separatory funnel. 
The solution is now cooled and more hydrochloric 
acid added. This throws out the impure sali- 
cylic acid. 

The impure acid is collected by fil- 
tration and is dried. Yield 44 gr. or 16;^ of 
the theoretical. 

With some modifications this is the 
Sohmitt method of preparation of salicylic acid. 



30. 



EZPERILffiKTAI RUKS. (1st Run) 

lEO gr. of sodium hydroxide were ais- 
solved in an equal amount of water and mixed into 
260 gm. of phenol. This was evaporated at 140°C 
and 14" vacuum. 350 grams of sodium phenate ob- 
tained. This was dark hrovai in color and very 
hygroscopic. The phenate was powdered up, placed 
in under a pressure of 10 Ihs., which was increas- 
ed to 50 Ihs. in the course of half an hour. The 
autoclave "became very warm during the passage of 
carbon dioxide. This pressure was kept up for 
two hours, then it was removed and the contents 
of the autoclave examined. The mass was dark 
"brown in color and of a thick pasty consistency; 
it smelt strongly of phenol. The cover ".vat re- 
placed and 50 lbs, of pressure applied from the 
oar'Lon dioxide tank. The autoclave was placed 
in a paraffin bath and heated for two hours at 
130°-145°C. During this heating the pressure 
inside the autoclave went up to 60 lbs. 

At the end of the two hours the auto- 



31, 



clave was allov;ed to cool off, and the contents 
were examined. The mass v.as of a dark brov.n 
color, moist and covered on top with fine cry- 
stals of phenol. This was transferred to an 
evaporating dish and dissolved in hot water. A 
little hydrochloric acid threw dov.Ti the tarry 
matter which was separated out. The remaining 
part was tested with ferric chloride after the 
excess of hydrochloric acid was neutralized with 
calcium cartonate. The test did not show the 
presence of salicylate. 



32. 



EZPERIIJIEKTAI RUNS. (End Run) 

The same amounts of phenol and sodium 
hydroxide used as in the previous run. Evapor- 
ated at 100°C and 18" vacuum. 

The sodium phenate obtained was light 
brovm in color and hygroscopic. It was poudered , 
placed in the autoclave and carton dioxide gas 
passed in at a pressure of 10 lbs. and within 
half an hour this was gradually increaeed to 60 
lbs. The autoclave became very warm. The press- 
ure was kept up for two hours, then removed and 
the contents examined. The mass was brown in 
color, moist and s;nelt of phenol. The cover was 
now replaced and 60 lbs. of pressure applied from 
the carbon dioxide tank. The autoclave was heat- 
ed for three hours at 150°-145°C. The pressure 
in the autoclave increased during heating to 70 
lbs. 

At the end of the three hours the auto- 
clave was allowed to cool off and the mass examined, 
It was brown in color, somewhat moist and covered 



with crystals of phenol. 

This was treated as in the first run, 
and the ferric chloride gave a very strong test. 
However, there v.as not enough salicylate present 
to allow of its isolation in a oure state. 



34. 



ESPSRIMEIITAL RUUS. (Srd Run) 

The same amounts of phenol tmd sodium 
hydroxide used. The mixture was evaporated at 
60°C and 22" vacuum. The sodium phenate obtain- 
ed v.as pinkish v.hite in color and slightly hy- 
groscopic. 

It v.as powdered and placed in the auto- 
clave. Carbon dioxide gas was passed in at a 
pressure of 5 Ihs. and the autoclave v,as cooled 
by means of running cold water, as descriced in 
Run 4. In the course of an hour the pressure 
was gradually increased to 70 lbs. and kept up 
for another hour. The pressure was now removed 
and the mass in the autoclave examined. It v.'as 
light in color, dry, porous and it had a faint 
odor of phenol. 

After the cover was replaced, 70 lbs. 
of pressure was applied from the caruon dioxide 
tank ana the autoclave heated at 120-1400G for 
four hours. 

After the autoclave had cooled off the 



35. 



mass was transferred to an evaporating dish. It 
was brownish gray in color, dry and had a faint 
odor of phenol. Hot v.-ater was added and after 
the tarry matter was separated out the impure 
salicylic acid was thrown out by another addit- 
ion of hydrochloric acid. [This was collected 
on the filter and dried. Yield 14 gr. or 4^. 



36, 



PURIi'ICATIOlI Oi' THE lUPUHE ACID. 

The impure acid is dissolved in "boil- 
ing v.-ater and then neutralii:ed v/ith calcium 
oartonate and allowed to cool. Calcium sali- 
cylate separates oat in hard glistening crystals. 
A fairly pure acid yields almost pure white cry- 
stals, hut an impure acid gives brov.nish cry- 
stals. A second crystallization is ootained from 
the mother liquor. 

The calcium salt is again crystallized 

from water, until a pure white salt is ohtaiii- 

ed. It is now decomposed with hydrochloric acid 

and the pure sclicylic acid is washed with a 

little cold v.ater and finally crystallized out 

from dilute aloohol. This gives a very pure 

salicylic acid in the form of large prismatic 

crystals. 

After this purification only 29 gr. 

of pure acid was octained. or 6.3;: of the theo- 
retical yield. 

The chief impurities found in impure 



37. 



acid are: phenol, creosotic acid due to impure 
phenol, para-hydroxy-benzoic acid and a-hydroxy- 
Iso-phthalic acid due to the presence of caustic 
BOda and to a too high or too low temperature 
in the manufacture. 

The presence of a small amount of Jm- 
puritiee causes the acid to crystallize from 
dilute alcohol in the form of a mass of inter- 
laced crystals instead of well defined large 
prisms. 

It is quite clear that with proper 
conditions present, the yield depends on the 
pressure. However, the highest pressure ob- 
tainahle with the equipment on hand v.as 75 lbs. 
per sq. in. , therefore no further runs were 
attem'oted. 



38. 



TEE CH3LII£'i?Ry OF THE SCffi.IITT LETHOD. 

The chemistry of preparation of sali- 
cylic acid by the method proposed by Schinitt 
was explained by S. Tijmstra jun. (Ber.1905, 
58, 1375-1365) 

Sodium phenate is prepared as in the 

Kolbe method 

C H OH * llaOH = C H OKa * H 
6 5 6 5 2 

When carbon dioxide is passed into 

the sodium phenate and heated to 120°-130°C 

under pressure the resulting product is ortho- 

BOdoxybenzoic acid (sodium phenoxide-ortho- 

carboxylic acid) 

OKa 

JQuH 
OUa.CgH^.COgH -- 



It is not identical with sodium sali- 
cylate. It has a greater dissociation tension 
than sodium salicylate. It slov?ly absorbs 
ammonia at ordinary temperatures. It is not 



S9. 



transformed into sodium salicylate when evapor- 
ated to dryness \\ith water. It changes complete- 
ly to sodium salicylate when dissolved in ace- 
tone. The ortho-sodoxyhenzoic acid, which is 
thus formed, on heating undergoes an isomeric 

change into sodium salicylate: 

OH 

COOlJa 

This shows that the C0„ enters direct- 

2 

ly into the nucleus. 

Y/hen sodium salicylate is heated in a 
closed tube for 2-12 hours at 248'^, it changes 
more or less completely into ortho-sodoxyhenzoic 
acid. 



40. 



CQKGIUSIOU. 

The proper v^orking co adit ions for 
the process are outlined under "Our Method 
of Preparation." 

However, for larger yields pressure 
up to 125 lbs. per so. in, or even higher 
should ce used. 

To use an enameled autoclave with 
a stirring device would he of decided advan- 
tage, because it would yield a purer and more 
uniform product and it would materially cut 
down the time necessary for the completion of 
the reaction. 

The yield as well as the quality of 
the product depends mainly on three requisites; 
the sodium phenate must not ce charred, it 
must be dry and well powdered; the carbon diox- 
ide must bo dry; the temperature must be 
closely controlled. 



41. 



RE?ESE^TCES . 
Neues HandwOrterlDuoh der Cheraie - 1890. 
Dictionnaire de Ghiinie - 1906. 
Thorp, Dictionary of Applied Chemistry, 7.4, - 1913. 

Die SyuthetiBchen Darstellimgsmethoden der 
Zohlenstoff-Verbindungen, Dr. Zarl Elbs - 1689. 

r/atts, Dictionary of Chemistry, V.5, - 1692. 

J. Chern Soc. 114. 11, 137-8. 

Ber. S. [Dijmstra, jun. , 1905, 36, 1375-65.